Electrooptical system



Sept. 13, 1949. w. H. T. HOLDEN 2,481,567

ELECTROOPTICAL SYSTEM Filed May 22, 1947 Patented Sept. 13, 1949 UNITED STATES TENT OFFICE ELECTROPTECAL SYSTEM Application May 22, 1947, Serial No. 749,725

(Cl. Z50-415) 19 Claims.

This invention relates to electrical control systems and more particularly to electro-optical systems.

An object of the invention is to provide an improved electrical` control system comprising a gaseous discharge device.

Another obect is to provide an improved method of controlling the firing of gaseous discharge trigger tubes.

In an example of practice of the invention a gaseous discharge device having a cold cathode, an anode, and a control electrode is connected in circuit with a load device anda source of alternating current voltage so that. the energization of the load device may be controlled by the illumination of a photoelectric tube. Increased sensitivity to light is obtained by so connecting the photoelectric cell in a circuit between the control electrode and the cathode of the gaseous discharge tube, that a condenser is charged by current ilowing through the phot electric cell during each half wave oi the alternating current voltage which makes the anode negative with respect to the cathode and the voltage due to such charge isv added to the alternating current voltage during each succeeding half wave which makes the anode positive with respect to the cathode to eventually produce a summation positive Voltage on the control electrode with respect to the cathode to trigger off the main discharge, or, in other words, to nre the gaseous discharge tube.

liny this example of practice ofV the invention the source of alternating current voltage is ccnnected in series with the energizing winding of a relay which serves as load device and the main discharge path of the gaseous tube. A resistive voltage divider is connected across the source of alternating current voltage` Across a portion of this voltage divider there is connected a condenser. a resistor and a photoelectric tube in series in the order named with the anode of the p-hotoelectric tube connected to the terminal or the voltage divider which is connected, to the cathode of the gaseous discharge tube. The junction of the series resistor and condenser is connected through another resistor to the control electrode oi the gaseousy discharge tube. The peak voltage which is impressed on this series arrangement of condenser, resistor and photoelectric tube from the voltage divider is insufficient alone to -fire the gaseous discharge tube even on a positive peak half wave. However, on each negative half wave when the photoelectric tube is illuminated, a charge is accumulated on the condenser Which is of.. a polarity tending to make the control electrode positive with respect to the cathode. This charge is trapped on the condenser because it leaks 01T during the positive half wave period very much more slowly than it is accumulated on the negative half `wave period. The voltage due to this accumulated charge is added to the positive half Wave of the alternating current voltage to make the control electrode more positive with respect to the cathode than it would be otherwise. This summation voltage therefore res the gaseous discharge trigger tube.

This system is extremely sensitive to illumination of the photoelectric tube. High voltage gaseous discharge tubes may be employed because the system is not dependent upon a high currentcarrying capacity of the photoelectric tube so that vacuum photoelectric tubes may be employed. For rapid action, the capacity of the condenser may be made small providing only that it is large enough to supply the transfer current for the gaseous discharge tube. The sensitivity to small illumination is dependent upon the leakage ci charge from the condenser during the positive half wave periods. One significant leakage path is between the control electrode andthe cathode within the gaseous discharge tubeA This leakage path determines the minimum illumination on which the gaseous tube will nre. The sensitivity may be reduced by connecting a resistor in shunt of the condenser. Y

In a further modified arrangement illustrative of this invention two gaseous discharge tubes are employed. The rst is a tube requiring low transfer current which is fired under control of a photoelectric tube as above described. A small condenser only is needed to supply such transfer current. The second is red by the firing of the iirst in such a manner that a voltage developed across a resistor by the main discharge current of the rst gaseous tube is addedv to a part of the positive half wave voltage of the alternating current voltage source to trigger off the second gaseous discharge tube.

The invention may be embodied in still other arrangements.

The invention will now be described more in detail having reference to the accompanying drawing.

Fig, 1 illustrates one embodiment of the invention comprising a single gaseous discharge tube.

Fig. 2 illustrates a second embodiment oi the invention comprising two gaseous discharge tubes.

Like elements in the several figures of the drawing are indicated by identical reference charac.- tersy Referring now to Fig. 1 of the drawing, a specific embodiment of the invention is illustrated in the form of an electro-optical control system. A gaseous discharge trigger tube 5 comprising a cold cathode 6, a control electrode 'I and an anode 5 is connected in circuit with a source of alternating current voltage 9 and a load device, such as a relay I El. One terminal of relay I is connected to one terminal of the source 9 by conductor II. rThe other terminal of relay I0 is connected to the anode 8. The cathode B is connected to the other terminal of source 9 by conductor I2. A voltage divider consisting of resistors I3 and I4 is connected across the alternating current voltage source S between conductors II and I2. Across resistor I4 there is connected condenser I5, resistor I6 and photoelectric tube I'I in series, the anode 23 of tube I'I being connected to conductor I2 and the upper terminal of condenser I5 being connected to the junction I8 of the joined terminels of resistors I3 and I4. The junction I9 between the joined terminals of condenser I5 and resistor I6 is connected by a resistor 20 to the control electrode 'I of gaseous discharge tube 5. By means of a double pole switch 2I a variable leakage resistor 22 may, if desired, be connected in shunt of condenser I5.

The peak voltage of the source 9 is set below the breakdown voltage of the discharge path between the cathode 6 and anode 8 of the gaseous discharge tube 5, when the condenser I5 is in discharged or almost discharged condition, that is, when the peak voltage across resistor I4 on the positive half wave only is impressed on the control electrode 'I to make it positive with respect to the cathode S. Under these conditions the gaseous tube 5 cannot re. With the switch 2I open the junction I 9 on the positive half wave assumes approximately the potential of the junction I8 which is positive with respect to the conductor I2 and cathode 6. There is some tendency for electrons to ilow from the cathode '6 to the control electrode l but no disruptive discharge occurs and the condenser I5 is only slightly charged with the lower plate negative with respect to the upper plate, that is, with a polarity to oppose the positive half wave voltage across resistor I4. With the switch 2l closed even a smaller charge accumulates on condenser I5. During the period of the positive half wave the photoelectric cell II is substantially blocked so that no current flows therethrough. During the period of the negative half wave of voltage of the source 9 there is obviously no tendency for the gaseous tube 5 to fire because the anode 8 is negative with respect to the cathode 6. Under these circumstances the junction I9 is negative with respect to conductor I2 and cathode 6 and there results only a very small flow of electrons from the control electrode I to the cathode 6 through the gaseous path within the tube 5 and any inherent leakage path between the control electrode 'I and the cathode G. Such flow of electrons tends to charge the condenser I5, making the lower plate positive with respect to the upper plate. Such charge, however, would not exceed an exceedingly small value because of the inherent leakage between the terminals of condenser I5 even with the switch 2I open and would be negligible if the switch 2I were closed to connect leakage resistor 22 in shunt of condenser 2l. VIhen junction I5 is negative with respect to conductor I2 there is a tendency for current flow through the photoelectric tube I 'I because the anode 23 is positive with respect to the cathode 24. However, if the tube I'I is in the dark, that is, not illuminated, no electron flow takes place and con-v denser 55 remains practically discharged so that'I discharge tube 5 is not fired even on positive half.' waves of the alternating current voltage from. source 9.

Conditions are quite different, however, when the photoelectric tube Il is illuminated even to a small amount. On the negative half wave of the alternating current voltage the junction I9, as hereinbefore mentioned, is negative with respect to the conductor I 2, that is, the anode 23 of photoelectric tube Il is positive with respect to the cathode 24. Electrons flow from the cathode 24 to the anode 23 which makes the lower plate of condenser i5 positive with respect to the upper plate. During the following positive half wave the voltage on condenser i5 is added to the voltage across resistor I4 to make the potential of control electrode more positive with respect to the cathode 6 than it otherwise would be. This charge on condenser I5 is substantially trapped during the positive half wave. However, if the illumination is large enough and the condenser small enough, the charge accumulated on condenser I5 may be great enough during a single negative half wave to produce a voltage on condenser I 5 which, when added to the peak voltage across resistor I4 on the followingr positive half wave, will re the gaseous discharge tube 5. On smaller illuminations the accumulation of increments of charge on condenser I5 during several negative half waves may be required to produce suflcient voltage to re the tube 5 on a following positive half wave.

From the foregoing description of the arrangement of Fig. 1, it is seen that a very sensitive electro-optical control circuit results from this invention. It will operate on both small and large illuminations. The minimum illumination required to fire the gaseous tube 5 is a function of the leakage conductance across the terminals of condenser I5. The number of negative half waves required to cause firing of the gaseous tube 5 with minimum illumination of photoelectric tube I1 is a function of the capacitance of the condenser i5. The minimum capacitance of the condenser i? is dependent upon the amount of transfer current required to re the gaseous tube 5. The resistance of resistor 2!) is a function of the time required to sustain the transfer current discharge to effect the main discharge. The leakage conductance of condenser I5 is a function of the conductance between control electrode 'I and cathode 6 of gaseous tube 5 and the value of resistor 22 when switch 2I is closed. As shown in Fig. 1, resistor 22 may be varied as desired.

It is to be noted that photoelectric tube Il functions as a current controller in a unilateral or one-way circuit. Electrons flow only from the cathode 24 to the anode 23 except for a normally insignificant amount of leakage conductance between the terminals of the tube. Dependent upon the results desired, it is seen from the foregoing description that other kinds of unilateral current controllers may be used.

In order to operate some types of load devices, a type of gaseous discharge device is required which itself requires a relatively high value of transfer current. This necessitates the use of a relatively high capacity condenser I5 which, in turn, reduces the sensitivity of the system for rapid action.

A modified form of circuit which overcomes the above-mentioned disadvantage of the arrangement of Fig. 1 is illustrated in Fig. 2. The relay 30 of Fig. 2 is of a type which requires a gaseous discharge tube 3I having a high value of transfer current to eiect the main discharge to operate the relay 30. The tube 3I comprises a cold cathode 32, a control electrode 33 and an anode 34. One terminal of relay is connected to one terminal of the source of alternating current voltage 9 by conductor II. The other terminal of relay 30 is connected to anode 34. Cathode 32 is connected to the other terminal of the alternating current voltage source 9 by conductor 35. A voltage divider consisting of resistor i3, potentiometer 36 and resistor 31 is connected across the alternating current voltage source 9 between conductors II and 35. A second gaseous discharge tube 38 having a low value of transfer current is used to effect the firing of gaseous discharge tube 3|. Tube 38 comprises a cold cathode 39, a control electrode 40, and an anode 4I. The anode 4I is connected to one terminal of alternating current voltage source 9 by conductor I l. The cathode 39 is connected to the junction 42 between the joined terminals of potentiometer 36 and resistor 31. The cathode 39 is also connected to control electrode 33 of gaseous tube 3l through resistor 43. The condenser I5, resistor i6, photoelectric tube I1, switch 2| and resistors 23 and `22 are arranged to control the firing of gaseous tube 38 in much the same manner that the same elements in Fig. 1 are arranged to control the firing of gaseous tube 5. The upper plate or" condenser I5 is connected to the junction 44 oi the joined terminals of resistor I3 and potentiometer 36. The anode 23 of photoelectric tube l1 may be connected by a three-position switch 45 to conductor when switch blade 46 is closed on contact 41, or to the movable contact 4S of potentiometer 36 when switch blade 46 is closed on contact 49, or to the junction 42 between the joined terminals of potentiometer 39 and resistor 31 when the switch blade 46 is closed on contact 50. The operation is much the same whether the switch blade 46 is closed on contacts 41, 49 or 50. In every case, when the photoelectric tube I1 is maintained dark the gaseous tube 36 is not red because the condenser I5 remains in a practically discharged condition with little or no voltage being developed across its terminals. However, when the photoelectric tube I 1 is illuminated, electrons flow from the cathode 24 to the anode 23 on the negative half waves of the voltage from the alternating current voltage source 9 and the junction I9 becomes positive with respect to the junction 44 due to the charge on condenser I5. During the positive half waves this voltage across condenser I5 is added to the voltage drop across potentiometer 36 making the control electrode 46 enough positive with respect to the cathode 39 of the gaseous tube 38 to fire the tube 38. The main discharge current of tube 38 is added to the normal current iiow through resistor 31 to cause a voltage drop across resistor 31 of sufcient amount to fire gaseous tube 3l. As soon as the gaseous path between theY control electrode 33 and cathode 32 breaks down, the discharge is sustained by current flowing through the main discharge path of gaseous tube 38 and resistor 43. This sustained discharge provides the transfer current for the gaseous tube 3l.

The connections through contacts 49 and 50 of switch 45 to movable contact 46 of potentiometer 36 and junction 42, respectively, are to insure operation of the circuit on high values of illumination of the photoelectric tube l1. With the anode 23 of photoelectric tube l1 connected to conductor 35 through switch blade 46 and switch contact 41 and the cathode 24 of photoelectric tube I1 highly illuminated, it might happen that the charge on condenser I5 would be sufficiently large to produce enough positive potential at junction I9 with respect to cathode 39 of gaseous tube 38 to cause a disruptive discharge between the control electrode 46 and cathode 39 before any or sufficient voltage from the positive half Wave could be impressed on the main discharge path of the gaseous tube 38 to cause it to re. Under these circumstances the gaseous tube 38 would fail to re, and the system as a whole would fail to function. This condition is prevented by closing switch blade 46 on contact 50. An even further reduction of charge of condenser I5 may be obtained and of an adjustable amount by closing switch blade 46 on switch contact 49.

In the arrangement of Fig. 2 the gaseous tube 38 may be prevented from firing even with the photoelectric tube I1 illuminated by leaving switch 45 open as shown. The tube 38 may be fired merely by closing the switch blade 46 to an appropriate one of contacts 41, 49 or 50. According to this method of operation, the photoelectric tube I1 acts merely as a unilateral or oneway current conducting device.

It is obvious from the foregoing description that other kinds of load devices may be substituted for the relays I0 and 30. The relays l0 and 30 are of the slow release type and will hold up on pulsating current such as flows through the main discharge paths of gaseous tubes 5 and 3l.

It has been found that with a gaseous tube requiring a relatively high transfer current, a system like that of Fig. 1 will function properly if the source 9 supplies a voltage of 120 volts and 60 cycles per second, if the root-mean-square voltage drop across resistor I4 is 50 volts or the peak voltage is '72 volts, and if the condenser I5 has a capacity of 0.001 microfarad. With this arrangement if the gaseous tube 5 is to re on the positive half wave immediately following the rst negative half Wave during which the photoelectric tube I1 becomes illuminated and a voltage of 25 volts across the condenser I5 is required, the photoelectric tube I1 must produce an average current of 3.125 milliamperes during the full negative half wave. The sensitivity of such an arrangement is relatively low. By using a gaseous tube requiring a relatively low transfer current, a much smaller condenser I5 may be used. It has been found that in an arrangement like that of Fig. 2 with a condenser having a capacitance of 30x10-l2 farad the phctoelectric tube I1 need supply a current of only 0.093'15X10-6 ampere or slightly less than 0.1 microampere. The examples of practice described hereinbefore are merely illustrative since many diierent embodiments of the invention are possible.

The invention may be embodied in a variety oi forms all of which come within the purview of the appended claims.

What is claimed is'.

l.. A photoelectric control system comprising a gaseous discharge trigger tube having a :cathode, an anode, and a control electrode, a source of alternating current voltage, a voltage divider connected across said source of voltage, a series circuit including a condenser and a photoelectric tube having a cathode and an anode connected across a portion of said voltage divider with the anode remote from said condenser in said series circuit, a conductive connection from a point in said vseries circuit intermediate said condenser and said photoelectric tube to said control electrode, a conductive connection from the cathode of said trigger tube to the portion of the voltage divider to which said photoelectric tube is connected, and a conductive connection from the anodeof said trigger tube to the portion of said voltage divider to which said photoelectric tube is not connected.

2. A photoelectric control system comprising a gaseous discharge trigger tube having a cathode, an anode, and a control electrode, a source of alternating current voltage, a voltage divider connected across said source of voltage, a series circuit including a condenser and a photoelectric tube having a cathode and an anode connected across a portion of said voltage divider with the `anode remote from said condenser in said series circuit, a conductive connection from a point in said series circuit intermediate condenser and said photoelectric tube to said control electrode, a conductive connection from the cathode of said trigger tube to the portion of the voltage divider to which said photoelectric tube is connected, a conductive connection from the anode of said trigger tube to the portion of said voltage divider -to which said photoeiectric tube is not connected, and means to connect a resistor in shunt of said condenser.

3. An electrical control system comprising a gaseous discharge tube having a cathode, anode and a control electrode, a source oi alternating current voltage, a series circuit including said source and the discharge path between said cathode and anode, and means including a condenser and an asymmetrically conductive device in a circuit connected between said controlr electrode and said cathode for charging said condenser through said asyrnmetrically conductive device during each half wave of the voltage from said source which makes said anode negative with respect to said cathode and during each fcllowing half wave from said source adding a voltage to the voltage of said condenser to make the control electrode positive with respect to said cathode in a manner adapted to cause a gaseous discharge between said control electrode and cathode to trigger oi the main discharge when the charge on said condenser is suiiiciently large.

4. An electrical control system comprising a gaseous discharge tube having a cathode, an anode and a control electrode, mea-ns to impress impulses of voltage on the discharge path between said cathode and anode with a polarity to ymake said anode positive with respect to said cathode, means including a condenser to impress impulses of voltage on the discharge path between said cathode and control electrode with a polarity to make said control electrode positive with respect to said cathode in phase effectively with said voltage impressed on said anode and cathode path, and means external to said discharge tube to produce a trapped charge on said condenser during the period between the impressing of impulses of voltage on said control electrode and cathode path with a polarity to increase the total voltage impressed on said control electrode and cathode path during the following period when an impulse of voltage is impressed on said control electrode and cathode path.

5. An electrical control system comprising a gaseous discharge tube having a cathode, an anode and a control electrode, means to impress impulses of voltage on the discharge Vpath be tween said cathode and anode lwith a polarity to make said anode `positive with respect to said cathode, means including a condenser to impress impulses of voltage on the discharge path between said cathode and control electrode with a polarity to make said control electrode positive with respect to said cathode in phase effectively with said voltage impressed on said anode and cathode path, and vmeans including a light Vsensitive electric device to produce a trapped charge on said condenser'during the period between the impressing of impulses of voltage on said control electrode and cathode path with a polarity to increase the total voltage impressed on said control electrode and cathode path during the following period when an impulse of voltage is impressed on said control electrode and cathode path.

6. An electrical control system comprising a gaseous discharge tube having a cathode, an anode and a control electrode, means to impress impulses of voltage on the discharge path between said cathode and anode with a polarity to make said anode positive Vwith respect to said cathode, means including a condenser to impress impulses of voitage on the vdischarge path between said cathode and control electrode lwith a polarity to make said control electrode positive with respect to said cathode in phase effectively with said voltiinpressed on said anode and cathode path, means including a vacuum -type photoelectric tube having a photo-emissive cathode and an anode to produce a trapped lcharge on said condenser during the period between the impressing of impulses of voltage 'on said control electrode and cathode path with a polarity to increase the total voltage impressed on -said control electrode and cathode path during the following period when an impulse of voltage is impressed on said control electrode and cathode path.

7. An electro-optical control system comprising a source of alternating current voltage, a gaseous discharge trigger tube including a cold cathode,

' anode, and a lcontrol electrode, a load device,

a series circuit including said load device and the main discharge path between said cathode anode connected across said source oi voltage, a voltage divider 'connected across said source of voltage, a condenser connected from an intermediate point of said Voltage divider to said control electrode, and a light sensitive electric device connected between said control electrode and the cathode of said trigger tube in such a manner as to constitute a high impedance when the voltage from said source makes the cathode of said trigger tube negative with respect to the anode of said trigger tube.

8. An electro-optical control system comprising a source of alternating current voltage, a gaseous discharge trigger tube including a cold cathode, an anode, and a control electrode, a load device, a series circuit including said load device and the main discharge path between said cathode and anode connected across said source of voltage, a

voltage divider connected across said source of voltage, a condenser connected from an intermediate point of said voltage divider to said control electrode, and a phot'oelectric tube having a cathode and an anode connected between said control electrode and the cathode of said trigger tube with said cathode of said photoelectric tube nearer to said control electrode.

9. An electro-optical control system comprising a source of alternating current voltage, a gaseous discharge trigger tube including a cold cathode, an anode, and a control electrode, a load device, a series circuit including said load device and the main discharge path between said cathode and anode connected across said source of voltage, a voltage divider connected across said source of voltage, a condenser connected from an intermediate point of said voltage divider to said control electrode, a photoelectric tube having a cathode and an anode connected between said control electrode and said cathode of said trigger tube with said cathode of said photoelectric tube nearer to said control electrode, and a resistor adapted to be connected in shunt of said condenser.

10. An electro-optical control system comprising a source of alternating current voltage, a gaseous discharge trigger tube including a cold cathode, an anode, and a control electrode, a load device, a series circuit including said load device and the main discharge path between said cathode and anode connected across said source of voltage, a voltage divider connected across said source of voltage, a condenser connected from an intermediate point of said voltage divider to said control electrode, a photoelectric tube having a cathode and an anode, said anode being connected to the cathode of said trigger tube, and a resistor connected between the cathode of said photoelectric tube and said control electrode.

l1. An electro-optical control system comprising a source of alternating current voltage, a gaseous discharge trigger tube including a cold cathode, an anode, and a control electrode, a load device, a series circuit including said load device and the main discharge path between said cathode andanode connected across said source of voltage, a voltage divider connected across said source of voltage, a condenser connected from an intermediate point of said voltage divider through a A"- resistor to said control electrode, and a light sensitive electric device connected between said control electrode and said cathode of said trigger tube in such a manner as to constitute a high impedance when the voltage from said source makes the cathode of said trigger tube negative with respect to the anode of said trigger tube.

12. An electro-optical control system. comprising a source of alternating current voltage, a gaseous discharge trigger tube including a cold cathode, an anode, and a control electrode, a load device, a series circuit including said load device and the main discharge path between said cathode and anode connected across said source of voltage, a voltage divider connected across said source of voltage, a condenser connected from an intermediate point .of said voltage divider through a resistor to said control electrode, and a photoelectric tube having a cathode and an anode, the cathode of said photoelectric tube being connected to the terminal of said condenser nearer said control electrode and the anode of said photoelectric tube being connected to the cathode of said trigger tube.

13. An electro-optical control system comprising a source of alternating current voltage, a rst gaseous discharge trigger tube having a cold cathode, an anode, and a control electrode, a voltage divider having a first and second terminal connected across said source of voltage, a conductive connection between the anode of said rst trigger tube and a rst terminal of said voltage divider, a condenser connected between a first intermediate point of said voltage divider and said control electrode oi said rst trigger tube, a conductive connection between the cathode of said first trigger tube and a second intermediate point on said voltage divider more remote from said first terminal than said rst intermediate point, a second gaseous discharge trigger tube having a cold cathode, an anode and a control electrode, a load device, a series circuit including said ioad device and the main discharge path between said cathode and anode of said second trigger tube connected across said voltage divider with the cathode of said second trigger tube conductively connected to said second terminal of said voltage divider, a conductive connection from the control electrode of said second trigger tube to the cathode of said first 'trigger tube, and a light sensitive electric device connected between said control electrode of said lirst trigger tube and a point of said voltage divider more remote from said first terminal than said rst intermediate point in such a manner as to constitute a high impedance when the voltage from said source makes the cathode of said first trigger tube negative with respect to the anode of said first trigger tube,

14. An electro-optical control system comprising a source of alternating current voltage, a first gaseous discharge trigger tube having a cold cathode, an anode, andk a control electrode, a voltage divider having a first and second terminal connected across said source of voltage, a conductive connection between the anode of said first trigger tube and a first terminal 4of said voltage divider, a condenser connected between a rst intermediate point of said voltage divider and said control electrode of said first trigger tube, a conductive connection between the cathode of said rst trigger tube and a second intermediate point on said voltage divider more remote from said first terminal than said first intermediate point, a second gaseous discharge trigger tube having a cold cathode, an anode and a control electrode, a load device, a series circuit including said load device and the main discharge path between said cathode and anode of said second trigger tube connected across said voltage divider with the cathode of said second trigger tube conductively connected to said second terminal of said voltage divider, a conductive connection from the control electrode of said second trigger tube to the cathode of said rst trigger tube, and a photoeiectric tube having a cathode and an anode connected between said control electrode of said iirst trigger tube and a point of said voltage divider more remote from said rst terminal than said rst intermediate point with said cathode of said photoelectric tube nearer said control electrode of said rst trigger tube.

15. An electro-optical control system comprising a source of alternating current voltage, a first gaseous discharge trigger tube having a cold cathode, an anode, and a control electrode, a voltage divider having a rst and a second terminal connected across said source of voltage, a conductive connection between the anode of said iirst trigger tube and a first terminal of said voltage divider, a condenser connected from a first intermediate point of said voltage divider through a resistor to said control electrode of said rst trigger tube, a conductive connection between the cathode of said first trigger tube and a second intermediate point on said voltage divider more remote from said first terminal than said first intermediate point, a second gaseous discharge trigger tube having a cold cathode, an anode and a control electrode, a series circuit including a resistor and a -photoelectric tube having a cathode and an anode, the cathode of said photoelectric tube being connectedA to `one terminal of said resistor and the other terminal of said resistor being connected to the terminal ci said condenser remote from said voltage divider, a load device, a series circuit including said load device and the mainl discharge path between said cathode and anode of said second trigger tube connected across said voltage divider with the cathode of said second trigger tube conductively connected to said second terminal of said voltage divider, a conductive connection from the control electrode of vsaid second trigger tube to the ca"`i ode of said rst trigger tube, and switching adapted to connect the anode of said photoelectric tube to either the cathode of said second trigger tube, or to said second intermediate point oi id voltage divider, or to an adjustable contact on said voltage divider movable between said first and second intermediate points of said voltage divider.

16. The method of ring a gaseous discharge trigger tube which comprises applying impulses of voltage to the terminals of the main gaseous discharge path of a trigger tube of an amplitude less than the voltage required to produce a disruptive discharge of said path in the absence of a disruptive discharge of the gaseous trigger applying impulses of voltage to the terminals of the gaseous trigger path while said impiuses of voltage are being applied to said main discharge path in a direction tending to produce a disruptive discharge of said gaseous trigger path but of an amplitude less than necssary to re said trigger tube, charging a condenser through a circuit exclusive of said trigger tube, and adding the voltage across the terminals of said condenser due to said charge to the impulses of voltage applied to said trigger path to produce a disruptive discharge of said gaseous trigger path to fire said trigger'tube.

17. The method of iiring a gaseous discharge trigger tube which comprises applying impulses of voltage to the terminals of the main gaseous discharge path of a trigger tube of an amplitude less than the voltage required to produce a disruptive discharge of said path in the absence of a disruptive discharge of the gaseous trigger path, applying impulses of voltage to the terminals of the gaseous trigger pathwhile said impulses of voltage are being applied to said main discharge path in a direction tending to produce a disruptive discharge of said gaseous trigger path but of an amplitude less than necessary to iire said trigger tube, charging a condenser through a predominantly one-Way conductive circuit exclusive of said trigger tube during periods when said impulses are not being applied to said gaseous rgger path, and adding the voltage across the terminals of said condenser due to said charge to the 12 impulses of voltage applied to said trigger path to produce a disruptive discharge of said gaseous trigger path to re said trigger tube.

18. The methodfof firing a gaseous discharge trigger tube which comprisesY applying impulses of voltage to the terminals of the main gaseous dischy rge path of a trigger tube of an amplitude less than the voltage required to produce a disruptive discharge ofy said path in the absence of a disruptive discharge of the gaseous trigger path, applying impulses of voltage tothe terminals of the gaseous trigger path while said impulses of voltage are being appliedv to said main discharge path in a direction tending to produceva disruptive discharge of said gaseous trigger path but of an amplitude less than necessary to fire said trigger tube, charging a condenser through a predominantly one-way conductive circuit entirely con trolied by radiantenergy, and adding the voltage gg across the terminals of said condenser due to said charge to the impulses of voltage appliedV to trigger' path to produce a disruptive discharge of said gaseous trigger path to fire said trigger tube. 19. The method o iiring a gaseous discharge i; tube v fhich comprises applying impulses voitage to the terminals of the main gaseous Le ci ak trigger tube of an amplitude ian the voltage required to produce a dis- Je discharge or" said path in the absence disruptive discharge of the gaseous trigger piying impulses of voltage to the terals of the gaseous trigger path while said imlses of voltage are being applied to said main ge path in a direction tending to produce tive discharge of said gaseous trigger .i out of an amplitude less than necessary to 'e said trigger tube, charging a condenser 40 cuit entirely controlledby light, and adding the voltage across the terminals oi said condenser due to said charge to the impulses of voltage appiied to said trigger path toproduce a disruptive discharge oisaid gaseous trigger path to re said trigger tube.

WILLIAM H. T. HOLDEN.

REFERENCES CITED The following references are of record in the 00 le of this patent:

UNITED STATES PATENTS Number Name Date 2,032,958 Stogoi Mar. 3, 1936 2,036,286 Long Apr. 7, 1936 2,034,136 Braden June 15, 1937 2,150,037 Shepard, Jn May 30, 1939 2,213,024 Cole Aug. 27, 1940 2,274,158 Penther Feb. 24, 1942 GO 2,411,078 Aubert NOV. 12, 1946 

